The present invention refers to an electronic thread travel monitoring device on a weaving machine provided with stationary weft yarn supply means and intermittently actuatable thread storing means arranged on the same side of the weaving machine. Generally, such monitoring devices serve for stopping the weaving machine in the event of yarn breaks.
Weaving machines of the type which are known as shuttleless weaving machines are used in practice on a large scale, e.g. gripper shuttle weaving machines, gripper weaving machines and jet weaving machines. With the first named gripper shuttle weaving machines, the weft or filling thread is inserted into the weaving shed by a flying gripper shuttle or projectile. On the gripper weaving machines, weft inserting devices are provided which are positively driven by rigid rapiers or flexible tapes.
Moreover, it is known to provide a thread storing device on such a weaving machine between the supply bobbin and the start position of the weft inserting device. On a thread winding drum of this thread storing device a winding of the weft yarn drawn off the supply bobbin is formed. During the weft or filling insertion, a yarn end is drawn from the drum and inserted into the weaving shed. The axial dimension of the winding is monitored by an electronic light barrier which controls the drive of the thread storing device. By means of such a thread storing device, the tension of the weft yarn which occurs during the weft insertion is reduced, such minimizing the danger of weft breaks within the shed.
However, it appears that yarn breaks may also occur between the supply bobbin and the thread storing device when thin places are present in the yarn. Now it is desirable to detect such yarn breaks as early as possible. Modern weaving machines are normally fitted with a weft monitor which detects breaks of the weft or filling thread only upon insertion in the weaving shed, and stops the machine. When such an event occurs with a gripper shuttle weaving machine provided with a dobby, firstly the yarn end inserted in the shed by the projectile must be manually removed. Then the dobby must be reset such that the last correctly entered weft thread is exposed in the shed, and thereupon a new weft end is to be drawn from the supply bobbin to and through the thread storing device and a following thread brake and yarn guides of the weaving machine. After all this, the weaving machine may be started again. The analogous procedure is still more time-consuming with a Jacquard machine.
Now when such an early yarn break in advance of the thread storing device can be detected and the weaving machine stopped in time, the said procedures at the weaving machine as well as at the dobby or Jacquard machine are avoided since the weft or filling thread is correctly inserted in the weaving shed. In this event, only the thread end connected to the supply bobbin must be drawn towards or eventually through the thread storing device and knotted to the other thread end.